Field of the Invention
The present invention relates to the production of absorbent sanitary articles, such as diapers, and relates to a method for producing a backsheet for absorbent sanitary articles. The invention also relates to an absorbent sanitary article including this backsheet.
Description of Prior Art
A diaper is normally composed of a permeable topsheet intended to come into contact with the user's skin when the diaper is worn, an impermeable backsheet and an absorbent core enclosed between the topsheet and the backsheet. Diapers normally have a back waist region and a front waist region that are closed around the user's waist by means of hook-and-loop fasteners, better known as Velcro© fastening devices. These fastening devices normally comprise a pair of closing wings that protrude laterally from the back waist region and which are releasably anchorable to a frontal tape applied on the outside of the backsheet at the front waist region. The frontal tape comprises a layer of loop-material forming the female part of the hook-and-loop closing device.
The loop-material of a hook-and-loop fastener is formed of a material, for example polypropylene, provided on an upper surface with micro-loops suitable for engaging with micro-hooks of the closing wings. The loop-material is normally fixed to a support typically consisting of a film of plastic material or of a non-woven polypropylene or the like.
EP-A-2540272 describes a multi-layer material for front panels of diapers, comprising a support formed of a polyolefinic film and a layer of loop-material formed by a non-woven polyolefinic material. The support and the layer of loop-material are secured together by glue.
In conventional solutions, the frontal tape formed of the loop-material and the respective support is cut and is applied to the outside of the backsheet level with the front waist region. The frontal tape is applied to the backsheet by means of glue or by ultrasound welding. Welding is generally not suitable because it can compromise the impermeability of the backsheet.
The backsheet of a diaper is a multi-layer composite structure including an impermeable film inside and a layer of outer non-woven material applied to the impermeable film by means of a layer of glue. In these cases, the frontal tape is applied on the outside of the non-woven layer of the backsheet, usually by means of a layer of glue. A drawback of this known solution is that the backsheet results in being rather thick and rigid at the frontal tape, given that in this area, the following are provided: an impermeable layer within the backsheet, a first layer of glue, an outer non-woven layer of the backsheet, a second layer of glue, the support of the frontal tape, a third layer of glue and the loop-material of the frontal tape.
In principle, it is possible to choose a material with preformed loops, similar to the “loop”-material of a Velcro® closure. A preformed loop-material for use in disposable articles can be of the type described in U.S. Pat. No. 5,611,791 by 3M, which describes a relatively thin non-woven material that is corrugated to have the loop-structure. This material is ready to be applied, typically with an adhesive layer, to the backsheet. This solution, however, would be very expensive for disposable items.
EP 2636782 A1 by Aplix Inc. describes a non-woven composite material forming a loop-material for a hook-and-loop closure. A fibrous material is laminated to a substrate. The fibrous material becomes a loop-material after welding of the precursor fibrous material to the substrate. The welding is carried out in areas with a pattern that has the dual purpose of creating three-dimensionality in the surface of the precursor, making it suitable for engaging with the hooks, and of stabilizing it, so that the hooks do not tear the fibers when loaded.